Projection display and lack of brightness uniformity compensation method

Abstract

It is an object of the present invention to correct brightness irregularities of color lights. A projection display apparatus includes a light source that emits light, DMs that divide the light emitted from the light source into a plurality of color lights, LCDs associated respectively with the color lights separated by the separating means, for modulating the color lights depending on an image signal, an XDP that combines the color lights modulated respectively by the LCDs, and a projection lens that projects light combined by the XDP. The projection display apparatus holds correction values for correcting brightness irregularities of the color lights which are caused by the prism. In response to the image signal received thereby, the projection display apparatus determines a plurality of brightness correction values to correct the brightness at the right and left ends of the combined light depending on the correction values, and corrects the image signal in order to correct each of the pixels represented by the image signal depending on the brightness correction values.

1 . A projection display apparatus comprising:
 a light source that emits light;   separating means that divides the light emitted from said light source into a plurality of color lights;   modulators associated respectively with the color lights separated by said separating means, for modulating the color lights depending on an image signal;   a prism that combines the color lights modulated respectively by said modulators;   a projection lens that projects light combined by said prism;   holding means that holds correction values for correcting brightness irregularities of the color lights which are caused by said prism; and   correcting means that, in response to the image signal received thereby, determines a plurality of brightness correction values to correct the brightnesses at right and left ends of the combined light depending on the correction values held by said holding means, and corrects said image signal in order to correct each of pixels represented by said image signal depending on said brightness correction values.   
     
     
         2 . The projection display apparatus according to  claim 1 , wherein said holding means holds a correction value for red and a correction value for blue; and
 said correcting means lowers the level of said image signal depending on a maximum value among the absolute values of the correction values held by said holding means, and corrects said image signal depending on said brightness correction values with respect to each of the correction values.   
     
     
         3 . The projection display apparatus according to  claim 2 , wherein said correcting means determines said brightness correction values by multiplying the distance between each of pixels represented by said image signal and a reference pixel by the correction values. 
     
     
         4 . The projection display apparatus according to  claim 1 , wherein said holding means holds first and second green correction values as the correction values; and
 said correcting means determines a first brightness correction value by multiplying the distance between each pixel on the left side of a central pixel of said pixels and said central pixel by the first green correction value, determines a second brightness correction value by multiplying the distance between each pixel on the right side of the central pixel and said central pixel by the second green correction value, and corrects said image signal depending on the first and second brightness correction values.   
     
     
         5 . A brightness irregularity correcting method for a projection display apparatus including a light source that emits light, separating means that divides the light emitted from said light source into a plurality of color lights, modulators associated respectively with the color lights separated by said separating means, for modulating the color lights depending on an image signal, a prism that combines the color lights modulated respectively by said modulators, and a projection lens that projects light combined by said prism, said brightness irregularity correcting method comprising:
 holding correction values for correcting brightness irregularities of the color lights which are caused by said prism, in holding means; and   in response to the image signal, determining a plurality of brightness correction values to correct the brightnesses at right and left ends of the combined light depending on the correction values held by said holding means, and correcting said image signal in order to correct each of pixels represented by said image signal depending on said brightness correction values.   
     
     
         6 . The brightness irregularity correcting method according to  claim 5 , wherein said holding correction values in the holding means includes holding a correction value for red and a correction value for blue in said holding means; and
 said correcting said image signal includes lowering the level of said image signal depending on a maximum value among the absolute values of the correction values held by said holding means, and correcting said image signal depending on said brightness correction values with respect to each of the correction values.   
     
     
         7 . The projection display apparatus according to  claim 2 , wherein said holding means holds first and second green correction values as the correction values; and
 said correcting means determines a first brightness correction value by multiplying the distance between each pixel on the left side of a central pixel of said pixels and said central pixel by the first green correction value, determines a second brightness correction value by multiplying the distance between each pixel on the right side of the central pixel and said central pixel by the second green correction value, and corrects said image signal depending on the first and second brightness correction values.   
     
     
         8 . The projection display apparatus according to  claim 3 , wherein said holding means holds first and second green correction values as the correction values; and
 said correcting means determines a first brightness correction value by multiplying the distance between each pixel on the left side of a central pixel of said pixels and said central pixel by the first green correction value, determines a second brightness correction value by multiplying the distance between each pixel on the right side of the central pixel and said central pixel by the second green correction value, and corrects said image signal depending on the first and second brightness correction values.